IEC 63522-18:2025

Electrical relays – Tests and measurements – Part 18: Thermal resistance of the coil

IEC 63522-18:2025 This part of IEC 63522 is used for testing along with the appropriate severities and conditions for measurements and tests designed to assess the ability of DUTs to perform under expected conditions of transportation, storage and all aspects of operational use. The object of this test is to determine the thermal resistance of the relay coil.

Relais électriques - Essais et mesurages - Partie 18: Résistance thermique de la bobine

IEC 63522-18:2025 La présente partie de l'IEC 63522 traite des essais ainsi que des sévérités et conditions appropriées pour les mesurages et essais destinés à évaluer l'aptitude de DUT à fonctionner dans des conditions prévues de transport, de stockage, et de tous les aspects d'utilisation opérationnelle. L'objet de cet essai est de déterminer la résistance thermique de la bobine du relais.

General Information

• Status: Published
• Publication Date: 20-May-2025
• ICS: 29.120.70 - Relays
• Technical Committee: TC 94 - Electrical relays
• Drafting Committee: WG 3 - TC 94/WG 3
• Current Stage: PPUB - Publication issued
• Start Date: 21-May-2025
• Completion Date: 28-Feb-2025

Standards Content (Sample)

IEC 63522-18 ®
Edition 1.0 2025-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical relays – Tests and measurements –
Part 18: Thermal resistance of the coil

Relais électriques – Essais et mesurages –
Partie 18: Résistance thermique de la bobine
ICS 29.120.70  ISBN 978-2-8327-0403-5

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– 2 – IEC 63522-18:2025 © IEC 2025
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Test procedure . 6
4.1 Purpose . 6
4.2 Procedure . 6
4.3 Conditions . 7
5 Evaluation . 7
5.1 General . 7
5.2 Test report . 7
Bibliography . 8

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL RELAYS –
TESTS AND MEASUREMENTS –
Part 18: Thermal resistance of the coil

FOREWORD
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IEC 63522-18 has been prepared by IEC technical committee 94: Electrical relays. It is an
International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
94/1060/FDIS 94/1111/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

– 4 – IEC 63522-18:2025 © IEC 2025
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts of IEC 63522 series, published under the general title Electrical relays – Tests
and measurements, can be found on the IEC website.
This International Standard is to be used in conjunction with IEC 63522-0:– .
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
___________
Under preparation. Stage at the time of publication: IEC CDV 63522-0:2024.

ELECTRICAL RELAYS –
TESTS AND MEASUREMENTS –
Part 18: Thermal resistance of the coil

1 Scope
This part of IEC 63522 is used for testing along with the appropriate severities and conditions
for measurements and tests designed to assess the ability of DUTs to perform under expected
conditions of transportation, storage and all aspects of operational use.
The object of this test is to determine the thermal resistance of the relay coil.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 63522-0:─ , Electrical relays – Tests and measurements – Part 0: Testing – General and
guidance
IEC 63522-10:─ , Electrical relays – Tests and measurements – Part −10: Heating
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 63522-0 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at https://www.iso.org/obp
3.1
thermal resistance
quotient of the temperature rise of the relay coil by the input power, measured after a period
long enough to reach thermal equilibrium
Note 1 to entry: The abbreviation for the thermal resistance is R .
th
Note 2 to entry: The thermal resistance usually is given in kelvins per watt.
[IEC 60050-444:2002, 444-02-17, modified – Addition of a new Note 1 to entry.]
___________
Under preparation. Stage at the time of publication: IEC CDV 63522-0:2024.
Under preparation. Stage at the time of publication: IEC FDIS 63522-10:2024.

– 6 – IEC 63522-18:2025 © IEC 2025
4 Test procedure
4.1 Purpose
The purpose of the thermal resistance test is to determine whether the temperature of the relay
coil is within the specified limits.
NOTE The thermal resistance is a heat property and consists of a measurement of the temperature difference by
which an object or material resists a heat flow. In conjunction with the heating test, this supports the understanding
of the heat generation of the relay. The heating test is the only evaluation method and can be used for any limits.
4.2 Procedure
The relay shall be assembled and mounted according to IEC 63522-10:–, Annex A, or as
specified by the manufacturer. The relay shall be energized successively at four values
approximately equally distributed throughout its operative range, and the temperature rise shall
be determined for each of them after the thermal equilibrium has been reached. All
measurements shall be made at a constant ambient temperature and the relay shall be
protected from draughts, solar irradiation and the like.
The temperature rise shall, for coils made of one or more materials, be calculated by the
formula:

RR− 1
wa
∆t t+ [K]

w a
R α
a0
where
Δt is the average temperature rise;
w
R is the resistance of the coil in thermal equilibrium;
w
R is the resistance of the coil at ambient temperature;
a
t is the ambient temperature;
a
α is the temperature coefficient of the resistivity of the conductor material at 0 °C.
This formula can be held valid for temperatures between 0 °C and 120 °C.
For copper, the formula below is used:
-1
α = [K ]
234,5
NOTE For other wire materials, the factor is chosen accordingly.
From the temperature rise, the thermal resistance is calculated by the formula below:
Δt
w
R = [K/W]
th
P
w
where
R is the abbreviation for the thermal resistance;
th
P is the value of the power supplied to the coil at thermal equilibrium.
w
The value to be compared with the specified value is, unless otherwise specified by the
manufacturer, the avera
...